In general, a conventional elevator rope for mid-rise/high-rise buildings is composed of eight outer layer strands and a center (independent wire rope core (IWRC) or fiber). Usually, products to which fiber has been applied are used for main traction, and products to which IWRC has been applied are used in governors.
However, as a high safety factor is needed for use in super high-rise buildings, higher breaking load is required, compared to the conventional elevator rope having a fiber center. Although the strength of wires may be improved in order to obtain high breaking load, due to characteristics of elevator ropes, main traction ropes cause friction with traction sheaves, and thus, there is a limit to increasing the strength of wires used to form elevator ropes. That is, the higher the strength of wires, the shorter the life of sheaves (normally, the hardness of wires contacting sheaves is less than that of the sheaves, and the wires maintain Vickers hardness at about 450±30), and accordingly, the IWRC is used instead of the fiber center.
As described above, although elevator ropes for super high-rise buildings, to which the IWRC has been applied, are used, eight outer layer strands are still used currently as in conventional elevator ropes for mid-rise/high-rise buildings. For safe running in times of high-speed running of elevators in super high-rise buildings, elevator ropes are required to be more structurally stabilized.